BACTERIA-ENGINEERED VESICLES FOR CANCER IMMUNOTHERAPY: FROM IMMUNOMODULATION IN VITRO TO ANTI-TUMOR EFFECTS IN MELANOMA MODELS

Abstract

Bacterial vesicles hold immense potential in various biomedical fields. Among these, outer membrane vesicles (OMVs) produced by Gram-negative bacteria are the most extensively studied. While the exact mechanism of OMV production remains unclear, numerous environmental factors have been shown to influence both their yield and composition. In this study, we investigated the effect of three different antimicrobial families on OMV production by E. coli. Interestingly, antimicrobials within the same family did not provide the same effects on OMV yield, suggesting that OMV production may not directly correlate with the antimicrobial mechanism of action. OMVs have demonstrated tumor-inhibitory activity in multiple mouse tumor models. However, their potential toxicity poses a significant challenge, as OMVs have been shown to cause mortality in mice. To address this limitation, we developed bacteria-engineered vesicles (BEVs) as a safer alternative to OMVs. In vitro assays, BEVs effectively repolarized pro-tumor macrophages (M2) to the anti-tumor phenotype (M1) and promoted dendritic cell maturation. Additionally, BEVs were shown to serve as a versatile platform for antigen peptide display, with the displayed peptides not interfering with BEVs\u27 inherent immunomodulatory activity. We further evaluated the anti-tumor efficacy of BEVs in a B16F10 melanoma model. Intravenous administration of BEVs significantly inhibited tumor growth and elicited robust immune responses. Flow cytometry analysis of spleen and lymph node samples from BEV-treated mice revealed an anti-tumor immune response, including elevated M1/M2 macrophage ratio and an increased population of CD8+ T cells